Pretty much all the current crop of smart tvs use HTML as their primary app platform. It's pretty consistently WebKit with a few custom integration points for TV specific functions. For all intents and purposes there is already a consistent open platform for apps on TVs
I own a small agency who builds apps for these platforms we can hit LG/Samsung/Panasonic/Sharp/Sony tvs with a single code base now. There are still a few outlier platforms like Yahoo Roku etc but HTML now gets us ~80% of the market.
Awesome to hear that. I've long suspected that TV was a more appropriate for HTML5 than mobile, precisely because the remote input is much closer to traditional computing than touch. Clicker.tv made a TV-centric web-app several years ago that works wonderfully.
If you have some time to write about it, I'd love to hear more about how these systems work, are they packaged or delivered over http? Do you use <video>?
